Fragments

The surviving fragments of Heraclitus's philosophical writing — preserved in quotations by later writers — containing his doctrine of universal flux, the unity of opposites, and the Logos — the most philosophically dense collection of pre-Socratic philosophy.

Creates the flux doctrine and the Logos concept — Heraclitus's fragments ('You cannot step into the same river twice'; 'Everything flows'; 'The way up and the way down are one and the same') are the most philosophically dense pre-Socratic writing and the origin of the Logos concept that later became central to both Stoicism and Christian theology.